Output for a desugared tree (sourceOutput == false) thus cannot be compiled. Output for (sourceOutput == true) is correct so this may be considered a non-issue.

enum Foo {AA, BB, CC { void m() {} }; void m() {};}

Generates ---

enum Foo {
    /*public static final*/ AA /* = new Foo() */,
    /*public static final*/ BB /* = new Foo() */,
    /*public static final*/ CC /* = new Foo()/*enum*/{
        
        void m() {
        }
    } */;
    
    void m() {
    }
}

Cause is

    public void visitVarDef(JCVariableDecl tree) {
...
            if ((tree.mods.flags & ENUM) != 0) {
...
                    print(" /* = ");
                    printExpr(tree.init);
                    print(" */");
                }